.TH std::enable_shared_from_this::shared_from_this 3 "2024.06.10" "http://cppreference.com" "C++ Standard Libary"
.SH NAME
std::enable_shared_from_this::shared_from_this \- std::enable_shared_from_this::shared_from_this

.SH Synopsis
   std::shared_ptr<T> shared_from_this();             \fB(1)\fP \fI(since C++11)\fP
   std::shared_ptr<T const> shared_from_this() const; \fB(2)\fP \fI(since C++11)\fP

   Returns a std::shared_ptr<T> that shares ownership of *this with all existing
   std::shared_ptr that refer to *this.

   Effectively executes std::shared_ptr<T>(weak_this), where weak-this is the
   exposition-only mutable std::weak_ptr<T> member of enable_shared_from_this.

.SH Return value

   std::shared_ptr<T> that shares ownership of *this with pre-existing
   std::shared_ptrs.

.SH Exceptions

   If shared_from_this is called on an object that is not previously shared by
   std::shared_ptr, std::bad_weak_ptr is thrown (by the shared_ptr constructor from a
   default-constructed weak-this).

.SH Example


// Run this code

 #include <iostream>
 #include <memory>

 struct Foo : public std::enable_shared_from_this<Foo>
 {
     Foo() { std::cout << "Foo::Foo\\n"; }
     ~Foo() { std::cout << "Foo::~Foo\\n"; }
     std::shared_ptr<Foo> getFoo() { return shared_from_this(); }
 };

 int main()
 {
     Foo *f = new Foo;
     std::shared_ptr<Foo> pf1;

     {
         std::shared_ptr<Foo> pf2(f);
         pf1 = pf2->getFoo(); // shares ownership of object with pf2
     }

     std::cout << "pf2 is gone\\n";
 }

.SH Output:

 Foo::Foo
 pf2 is gone
 Foo::~Foo

   Defect reports

   The following behavior-changing defect reports were applied retroactively to
   previously published C++ standards.

      DR    Applied to        Behavior as published              Correct behavior
                       calling shared_from_this on an
   LWG 2529 C++11      unshared object was undefined        std::bad_weak_ptr is thrown
                       behavior

.SH See also

   shared_ptr smart pointer with shared object ownership semantics
   \fI(C++11)\fP    \fI(class template)\fP
